[PATCH v9 8/8] KVM: Enable and expose KVM_MEM_PRIVATE

Chao Peng
2022-10-25T15:22:28Z

Expose KVM_MEM_PRIVATE and memslot fields restricted_fd/offset to
userspace. KVM register/unregister private memslot to fd-based
memory backing store and responses to invalidation event from
restrictedmem_notifier to zap the existing memory mappings in the
secondary page table.

Whether KVM_MEM_PRIVATE is actually exposed to userspace is determined
by architecture code which can turn on it by overriding the default
kvm_arch_has_private_mem().

A 'kvm' reference is added in memslot structure since in
restrictedmem_notifier callback we can only obtain a memslot reference
but 'kvm' is needed to do the zapping.

Co-developed-by: Yu Zhang <yu.c.zhang@linux.intel.com>
Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com>
Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
---
include/linux/kvm_host.h | 3 +-
virt/kvm/kvm_main.c | 174 +++++++++++++++++++++++++++++++++++++--
2 files changed, 171 insertions(+), 6 deletions(-)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 69300fc6d572..e27d62c30484 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -246,7 +246,7 @@ int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu);
#endif

-#if defined(KVM_ARCH_WANT_MMU_NOTIFIER) || defined(CONFIG_KVM_GENERIC_PRIVATE_MEM)
+#if defined(KVM_ARCH_WANT_MMU_NOTIFIER) || defined(CONFIG_HAVE_KVM_RESTRICTED_MEM)
struct kvm_gfn_range {
struct kvm_memory_slot *slot;
gfn_t start;
@@ -583,6 +583,7 @@ struct kvm_memory_slot {
struct file *restricted_file;
loff_t restricted_offset;
struct restrictedmem_notifier notifier;
+ struct kvm *kvm;
};

static inline bool kvm_slot_can_be_private(const struct kvm_memory_slot *slot)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 13a37b4d9e97..dae6a2c196ad 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1028,6 +1028,111 @@ static int kvm_vm_ioctl_set_mem_attr(struct kvm *kvm, gpa_t gpa, gpa_t size,
}
#endif /* CONFIG_KVM_GENERIC_PRIVATE_MEM */

+#ifdef CONFIG_HAVE_KVM_RESTRICTED_MEM
+static bool restrictedmem_range_is_valid(struct kvm_memory_slot *slot,
+ pgoff_t start, pgoff_t end,
+ gfn_t *gfn_start, gfn_t *gfn_end)
+{
+ unsigned long base_pgoff = slot->restricted_offset >> PAGE_SHIFT;
+
+ if (start > base_pgoff)
+ *gfn_start = slot->base_gfn + start - base_pgoff;
+ else
+ *gfn_start = slot->base_gfn;
+
+ if (end < base_pgoff + slot->npages)
+ *gfn_end = slot->base_gfn + end - base_pgoff;
+ else
+ *gfn_end = slot->base_gfn + slot->npages;
+
+ if (*gfn_start >= *gfn_end)
+ return false;
+
+ return true;
+}
+
+static void kvm_restrictedmem_invalidate_begin(struct restrictedmem_notifier *notifier,
+ pgoff_t start, pgoff_t end)
+{
+ struct kvm_memory_slot *slot = container_of(notifier,
+ struct kvm_memory_slot,
+ notifier);
+ struct kvm *kvm = slot->kvm;
+ gfn_t gfn_start, gfn_end;
+ struct kvm_gfn_range gfn_range;
+ int idx;
+
+ if (!restrictedmem_range_is_valid(slot, start, end,
+ &gfn_start, &gfn_end))
+ return;
+
+ idx = srcu_read_lock(&kvm->srcu);
+ KVM_MMU_LOCK(kvm);
+
+ kvm_mmu_invalidate_begin(kvm, gfn_start, gfn_end);
+
+ gfn_range.start = gfn_start;
+ gfn_range.end = gfn_end;
+ gfn_range.slot = slot;
+ gfn_range.pte = __pte(0);
+ gfn_range.may_block = true;
+
+ if (kvm_unmap_gfn_range(kvm, &gfn_range))
+ kvm_flush_remote_tlbs(kvm);
+
+ KVM_MMU_UNLOCK(kvm);
+ srcu_read_unlock(&kvm->srcu, idx);
+}
+
+static void kvm_restrictedmem_invalidate_end(struct restrictedmem_notifier *notifier,
+ pgoff_t start, pgoff_t end)
+{
+ struct kvm_memory_slot *slot = container_of(notifier,
+ struct kvm_memory_slot,
+ notifier);
+ struct kvm *kvm = slot->kvm;
+ gfn_t gfn_start, gfn_end;
+
+ if (!restrictedmem_range_is_valid(slot, start, end,
+ &gfn_start, &gfn_end))
+ return;
+
+ KVM_MMU_LOCK(kvm);
+ kvm_mmu_invalidate_end(kvm, gfn_start, gfn_end);
+ KVM_MMU_UNLOCK(kvm);
+}
+
+static struct restrictedmem_notifier_ops kvm_restrictedmem_notifier_ops = {
+ .invalidate_start = kvm_restrictedmem_invalidate_begin,
+ .invalidate_end = kvm_restrictedmem_invalidate_end,
+};
+
+static inline void kvm_restrictedmem_register(struct kvm_memory_slot *slot)
+{
+ slot->notifier.ops = &kvm_restrictedmem_notifier_ops;
+ restrictedmem_register_notifier(slot->restricted_file, &slot->notifier);
+}
+
+static inline void kvm_restrictedmem_unregister(struct kvm_memory_slot *slot)
+{
+ restrictedmem_unregister_notifier(slot->restricted_file,
+ &slot->notifier);
+}
+
+#else /* !CONFIG_HAVE_KVM_RESTRICTED_MEM */
+
+static inline void kvm_restrictedmem_register(struct kvm_memory_slot *slot)
+{
+ WARN_ON_ONCE(1);
+}
+
+static inline void kvm_restrictedmem_unregister(struct kvm_memory_slot *slot)
+{
+ WARN_ON_ONCE(1);
+}
+
+#endif /* CONFIG_HAVE_KVM_RESTRICTED_MEM */
+
#ifdef CONFIG_HAVE_KVM_PM_NOTIFIER
static int kvm_pm_notifier_call(struct notifier_block *bl,
unsigned long state,
@@ -1072,6 +1177,11 @@ static void kvm_destroy_dirty_bitmap(struct kvm_memory_slot *memslot)
/* This does not remove the slot from struct kvm_memslots data structures */
static void kvm_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot)
{
+ if (slot->flags & KVM_MEM_PRIVATE) {
+ kvm_restrictedmem_unregister(slot);
+ fput(slot->restricted_file);
+ }
+
kvm_destroy_dirty_bitmap(slot);

kvm_arch_free_memslot(kvm, slot);
@@ -1643,10 +1753,16 @@ bool __weak kvm_arch_has_private_mem(struct kvm *kvm)
return false;
}

-static int check_memory_region_flags(const struct kvm_user_mem_region *mem)
+static int check_memory_region_flags(struct kvm *kvm,
+ const struct kvm_user_mem_region *mem)
{
u32 valid_flags = KVM_MEM_LOG_DIRTY_PAGES;

+#ifdef CONFIG_KVM_GENERIC_PRIVATE_MEM
+ if (kvm_arch_has_private_mem(kvm))
+ valid_flags |= KVM_MEM_PRIVATE;
+#endif
+
#ifdef __KVM_HAVE_READONLY_MEM
valid_flags |= KVM_MEM_READONLY;
#endif
@@ -1722,6 +1838,9 @@ static int kvm_prepare_memory_region(struct kvm *kvm,
{
int r;

+ if (change == KVM_MR_CREATE && new->flags & KVM_MEM_PRIVATE)
+ kvm_restrictedmem_register(new);
+
/*
* If dirty logging is disabled, nullify the bitmap; the old bitmap
* will be freed on "commit". If logging is enabled in both old and
@@ -1750,6 +1869,9 @@ static int kvm_prepare_memory_region(struct kvm *kvm,
if (r && new && new->dirty_bitmap && (!old || !old->dirty_bitmap))
kvm_destroy_dirty_bitmap(new);

+ if (r && change == KVM_MR_CREATE && new->flags & KVM_MEM_PRIVATE)
+ kvm_restrictedmem_unregister(new);
+
return r;
}

@@ -2047,7 +2169,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
int as_id, id;
int r;

- r = check_memory_region_flags(mem);
+ r = check_memory_region_flags(kvm, mem);
if (r)
return r;

@@ -2066,6 +2188,10 @@ int __kvm_set_memory_region(struct kvm *kvm,
!access_ok((void __user *)(unsigned long)mem->userspace_addr,
mem->memory_size))
return -EINVAL;
+ if (mem->flags & KVM_MEM_PRIVATE &&
+ (mem->restricted_offset & (PAGE_SIZE - 1) ||
+ mem->restricted_offset > U64_MAX - mem->memory_size))
+ return -EINVAL;
if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_MEM_SLOTS_NUM)
return -EINVAL;
if (mem->guest_phys_addr + mem->memory_size < mem->guest_phys_addr)
@@ -2104,6 +2230,9 @@ int __kvm_set_memory_region(struct kvm *kvm,
if ((kvm->nr_memslot_pages + npages) < kvm->nr_memslot_pages)
return -EINVAL;
} else { /* Modify an existing slot. */
+ /* Private memslots are immutable, they can only be deleted. */
+ if (mem->flags & KVM_MEM_PRIVATE)
+ return -EINVAL;
if ((mem->userspace_addr != old->userspace_addr) ||
(npages != old->npages) ||
((mem->flags ^ old->flags) & KVM_MEM_READONLY))
@@ -2132,10 +2261,28 @@ int __kvm_set_memory_region(struct kvm *kvm,
new->npages = npages;
new->flags = mem->flags;
new->userspace_addr = mem->userspace_addr;
+ if (mem->flags & KVM_MEM_PRIVATE) {
+ new->restricted_file = fget(mem->restricted_fd);
+ if (!new->restricted_file ||
+ !file_is_restrictedmem(new->restricted_file)) {
+ r = -EINVAL;
+ goto out;
+ }
+ new->restricted_offset = mem->restricted_offset;
+ }
+
+ new->kvm = kvm;

r = kvm_set_memslot(kvm, old, new, change);
if (r)
- kfree(new);
+ goto out;
+
+ return 0;
+
+out:
+ if (new->restricted_file)
+ fput(new->restricted_file);
+ kfree(new);
return r;
}
EXPORT_SYMBOL_GPL(__kvm_set_memory_region);
@@ -4604,6 +4751,11 @@ static long kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg)
case KVM_CAP_BINARY_STATS_FD:
case KVM_CAP_SYSTEM_EVENT_DATA:
return 1;
+#ifdef CONFIG_KVM_GENERIC_PRIVATE_MEM
+ case KVM_CAP_PRIVATE_MEM:
+ return 1;
+#endif
+
default:
break;
}
@@ -4795,16 +4947,28 @@ static long kvm_vm_ioctl(struct file *filp,
}
case KVM_SET_USER_MEMORY_REGION: {
struct kvm_user_mem_region mem;
- unsigned long size = sizeof(struct kvm_userspace_memory_region);
+ unsigned int flags_offset = offsetof(typeof(mem), flags);
+ unsigned long size;
+ u32 flags;

kvm_sanity_check_user_mem_region_alias();

+ memset(&mem, 0, sizeof(mem));
+
r = -EFAULT;
+ if (get_user(flags, (u32 __user *)(argp + flags_offset)))
+ goto out;
+
+ if (flags & KVM_MEM_PRIVATE)
+ size = sizeof(struct kvm_userspace_memory_region_ext);
+ else
+ size = sizeof(struct kvm_userspace_memory_region);
+
if (copy_from_user(&mem, argp, size))
goto out;

r = -EINVAL;
- if (mem.flags & KVM_MEM_PRIVATE)
+ if ((flags ^ mem.flags) & KVM_MEM_PRIVATE)
goto out;

r = kvm_vm_ioctl_set_memory_region(kvm, &mem);
--
2.25.1